HISTORY AND NATURAL HISTORY 45 



at a time. And I have spent more hours wielding a 

 sturdy garden rake in swathe after swathe through 

 the short eel grass, very rarely pulling in more than 

 one starfish at a haul. 



Yet when a few brittle starfishes are placed in a 

 clean bucket of sea water they clump together like 

 magic (Plate III). In bare laboratory aquaria they 

 remain so clumped for weeks; in fact the aggrega- 

 tions become more compact as time goes on as the 

 animals bring back their extending arms and tuck 

 them into the mass. If, however, the aquaria are 

 dressed up by the introduction of eel grass so that 

 conditions approach those found in nature, the ag- 

 gregations disperse and the starfishes climb actively 

 about over the blades of the eel grass, feeding on 

 organisms and debris found on their surfaces. 



The idea that in clean laboratory dishes these star- 

 fishes are substituting each other for the missing eel 

 grass was obvious and easy to test. A kind of artifi- 

 cial eel grass was made of glass rods twisted in 

 various shapes so that they offered a supporting 

 framework for climbing in much the same way as 

 the true eel grass. So long as the rods remained the 

 starfishes clambered about over the meshwork or 

 hung motionless, usually isolated. If the rods were 

 removed they again clustered together. 



As I have said elsewhere, (3) it is a far cry from 



